The present invention relates to a series of novel fused-ring heterocyclic compounds which we have found to have valuable pharmaceutical activities, in particular anti-arrhythmic and diuretic effects, as well as improving brain function. The invention also provides processes for preparing these new compounds, pharmaceutical compositions containing them and methods of treating mammals, including humans, suffering from arrhythmia, urine retention and brain function disorders.
A variety of compounds are known having these properties. However, the known compounds are structurally unrelated to the compounds of the present invention. So far as we are aware, the closest prior art constitutes the compounds disclosed in J. Chem. Soc., Perkin Trans., 1(1), 97-101 (1980) and J. Med. Chem., 19(6), 792-797 (1976), but the compounds of the J. Chem. Soc. reference contain only 4 fused rings, in contrast to the 5 fused rings of the compounds of the present invention, and are disclosed only in the context of their synthesis and structures, whilst no practical use is suggested. The compounds of the J. Med. Chem. reference contain only 3 fused rings and are discussed as potential antidepressants; one of the synthetic routes for these compounds proceeds via a 4-ring compound, but no therapeutic use is disclosed for this intermediate.